CST – Computer Simulation Technology

Thermal Modeling of Heat Sinks

Efficient thermal management is critical for many electronic applications, and is a standard part of the design for components such as power electronics modules, multichip modules (MCM) and systems-on-packages (SOP). Heat sinks serve to transfer the generated heat of an electronic system away from the active and passive electronic components and toward the ambient environment. Temperature distributions and heat flows can be efficiently simulated using CST MPHYSICS® STUDIO (CST MPS). CST MPS offers both stationary and transient thermal simulation capabilities.



Figure 1: Heat sink with heat source

A heat sink carrying a heat source is shown in Figure 1. To model the interaction of the heat sink with the ambient environment, surface properties in terms of emissivity e (radiation) and heat transfer coefficient ...

h (convection) are assigned to the heat sink surface. For natural convection, h = 5 W/(m2·K) is a typical value.



Figure 2: Stationary heat spreading due to multidimensional conduction

Figure 2 shows the heat flow density. This is a measure of the spread of heat within the heat sink, and is related to the temperature distribution in Figure 3 by Fourier’s law.



Figure 3: Stationary temperature distribution of the heat sink, with measurement locations highlighted

The thermal simulation of the heat sink in Figure 1 was carried out assuming a thermal heat source of 21 watts. The results from this simulation were then compared with measurement results [1] at selected points on the heat sink, shown in Figure 3. The simulated and measured results are summarized in Table 1.

T1 / °C T2 / °C T3 / °C T4 / °C
Simulation 65.6 65.6 66.6 71.0
Measurement 66.3 65.7 67.8 69.8

Table 1: Measured and simulated temperatures at selected points

An excellent agreement was achieved, especially given the uncertainties of the measurements and the simulation. The simulation using the stationary thermal solver with a tetrahedral mesh took less than 2 minutes on a 2.67 GHz laptop with 4 GB RAM.

References

[1] Courtesy of Robert Bosch GmbH

Acknowledgment

The work described in this paper has received funding from the Federal Ministery of Education and Research under grant agreement no. 16N10943 (SOlar project).

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